| Titanium alloys, due to their high tensile strength, low density, and excellent corrosion resistance, have great potential in aerospace and medical implant applications. However, Ti alloy properties are very sensitive to oxygen content and readily oxidizes at high temperatures. Ab initio density functional theory calculations are utilized to study the atomistic mechanism of oxygen diffusion in titanium as well as the effect of substitutional solutes on oxygen diffusivity. Oxygen is found to reside at three interstitials in alpha-titanium, the octahedral, hexahedral, and crowdion sites. Transitions between these interstitial sites form a complex diffusion network in which almost all pathways contribute to diffusion. The interaction energy between oxygen and 45 substitutional solutes are calculated and used to predict how each solute changes oxygen diffusion through titanium. Additionally, the energetics and diffusion pathways for oxygen in 14 other hexagonal closed-packed (HCP) elements are studied, revealing that in most HCP systems the ground-state for oxygen is not the large octahedral site. |
